Why are the indexes of Scala tuples 1-based?

"Programming In Scala" explains that tuples'

_N numbers are one-based, instead of zero-based, because starting with 1 is a tradition set by other languages with statically typed tuples such as Haskell and ML

but this can hardly be called an explanation.

Why were tuples defined as 1-based in Haskell and ML in the first place? Are there any mathematical/programming benefits in having 1-based indexed tuples and not 0-based?

Thanks, Ori